An engine of air
The Andean Condor (Vultur gryphus) is the world's heaviest soaring bird, with a mass up to 15 kilograms. To stay aloft, it has mastered the art of energy-free flight. A 2020 study published in the Proceedings of the National Academy of Sciences attached custom data-loggers to eight condors in Patagonia to track their every movement. The results showed that these massive birds spend a mere 1% of their flight time flapping their wings. The vast majority of their time in the air is spent gliding on currents of rising air.
These aerial elevators, or "thermals," form when the sun heats the ground, creating bubbles of warm air that rise. Condors are experts at finding and circling within these columns to gain altitude with minimal effort. They also use "slope lift," which occurs when wind is deflected upwards by the mountain ridges of the Andes. This mastery of atmospheric physics is efficient and biologically necessary. The energy cost for a 15-kilogram bird to flap its wings is immense. The study found that 75% of a condor's flapping occurs during the initial takeoff, a high-cost activity that explains why they prefer to launch from high cliffs. Once airborne, their flight requires constant calculation of lift, drag, and energy conservation. One bird in the study flew for over five hours, covering 172 kilometers, without flapping its wings a single time.